The properties of garlic oil and garlic extracts, as described above, are believed to be derived from the presence of allyl polysulphides which are produced following the rupture of the cell walls of garlic during the crushing process. In this process, alliin is converted to allicin by an enzyme called allinase. Subsequently the allicin breaks down to form polysulphides as shown in scheme 1.

It is the allypolysulphides that are believed to give garlic extracts and garlic oil their biological activity and repellency properties. This biological activity of garlic is believed to be due to the allyl polysulphides acting as enzyme inhibitors, metal sequestrants, solvents which are active on cell membranes, respiratory inhibitors and as general antibiotics.